This type of object detecting apparatus is used for an opening and closing control system for a vehicle, which conducts the obstacle detection and controls the opening and closing body based on the detection result. In JP 2005-69867A (For example, Paragraph 37 to 56 and FIGS. 3 to 5), a technology regarding the object detecting apparatus is disclosed. The technology enables the apparatus to accurately detect a receipt time of a reflected wave even if the amplitude of reflected wave from an object varies. In JP 2005-69867A, an approximate line is obtained by approximating an upstroke of an envelope, using two intersecting points where an envelope obtained from the reflected wave intersects two threshold values, and a time that a value of the approximate line equals 0 volt is obtained. Even if the amplitude of the reflected wave varies and a gradient of the approximation line changes, the position of the zero cross point of the time does not move significantly. Thus, the position of the object is accurately detected.
However, reflected waves from multiple objects or noise components may superpose on the reflected wave to cause a rising portion in the upstroke of the envelope. In such a case, the approximate line is not accurately obtained and thus the time that the value of the approximate line equals 0 volt is not accurately detected. As a result, the detection precision of the object position deteriorates. In the view of the drawback, another technology that obtains the approximate line of the upstroke of the envelope more accurately is disclosed in JP 2007-315892A (For example, Paragraph 20 to 22 and 41 and FIGS. 6 and 10). According to JP 2007-315892A, a peak of the envelope is obtained and the approximate line is obtained by using the peak as the base. For example, the approximate line is obtained by least squares approximation using a voltage value in a predetermined period before the peak. Alternatively, the approximate line is obtained by least squares approximation using a voltage value ranging from 20 to 80 percent of the voltage value at the peak.
The foregoing technologies are excellent technologies for obtaining the accurate receipt time of the reflected wave and detecting the position of the object with high precision. However, as described above, reflected waves from multiple objects or noise components may superpose on the reflected wave, resulting in multiple inflection points in the upstroke of the envelope. In JP 2007-315892A, multiple inflection points may be included in a range which is subject to linear approximation and thus components, which are unnecessary for least squares approximation, are included. Therefore, limitations occur in improvement of the precision of the approximation line, the receipt time, and the objection position.
A need exists for an object detecting apparatus which is not susceptible to the drawback mentioned above.